Disk drives for storing electronic information are found in a wide variety of computer systems, including workstations, personal computers, and laptop and notebook computers. Such disk drives can be stand-alone units that are connected to a computer system by cable, or they can be internal units that occupy a slot, or bay, in the computer system. Digital cameras and other hand-held devices have relatively small bays in which to mount internal disk drives and other peripheral devices, as compared to the much larger bays available in most workstation and personal computer housings or even those found in laptop and notebook computers. The relatively small size of peripheral bays found in such hand-held devices can place significant constraints on the designer of internal disk drives for use in such devices. Techniques that address and overcome the problems associated with these size constraints are therefore important.
Disk drives often employ rotary actuators for positioning read/write heads of the disk drive over the surfaces of rotating storage media. Rotary actuators are used to carry the heads for magnetic disk drives, CD players, and optical drive devices. A rotary actuator has a pivot on bearings about which the actuator rotates to position the heads onto the desired track of the rotating storage medium. Magnetic flux for a rotary actuator is typically generated by its magnetic circuit comprising a return path assembly, a pair of magnets, and an actuator coil.
Typically, a flex circuit having a single dynamic lead is attached to a rotary actuator to (1) supply current to the actuator coil and (2) carry signals between the heads and an electric circuit board. One drawback of a single-lead flex circuit is that it is unnecessarily wide because it carries both the current supplied to the coil and the signals to and from the read/write heads on the same lead. Thus, it is desirable to provide a flex circuit for a rotary actuator that does not require as much vertical space as a single-lead flex circuit.
A common problem with carriage assemblies utilizing single-lead flex circuits is that the signals carried to and from the read/write heads are subject to electrical or induced noise from the line of current supplied to the coil. The relatively large amount of current supplied to the actuator coil creates a magnetic field around the wire carrying the current, resulting in induced noise that interferes with the relatively small electrical signals to and from the read/write heads. Because the current supplied to the coil and the signals to and from the heads are adjacent to each other in a single-lead flex circuit, induced noise is a substantial problem, especially where space is limited. Thus, it is desirable to provide a flex circuit for a rotary actuator that minimizes the induced noise that the line of current supplied to the coil imparts on the signals to and from the read/write heads.
One drawback with flex circuits for rotary actuators is that they take up valuable space adjacent to the circuit board on which they are mounted. Thus, it is desirable to provide a flex circuit for a rotary actuator that provides room for other flex circuit components to be mounted on the circuit board.
Another drawback with flex circuits for rotary actuators is that their design often requires the use of solder pads on both the top and bottom sides of the flex circuit. Such flex circuits are considerably more expensive to manufacture. Thus, in an effort minimize production costs, it is desirable to provide a flex circuit for a rotary actuator that does not require the use of solder pads on both the top and bottom sides of the flex circuit.